William Healy Sullivan arrived in Tehran on June, 8, 1977.Sullivan served as the U.S. ambassador to Iran from 1977 until 1979. During this time, he played an important role in communicating U.S. wishes to Mohammad Reza Shah, the second and last Pahlavi king. In the 1970s, the U.S. had unusually high military and economic links with Iran. Economically, billions of private U.S. dollars were invested in the country. Militarily, the U.S. had spent ten years redeeming its petrochemical dollars spent during the 1970s oil price boom by allowing the Shah's regime to purchase the most advanced non-nuclear weapons systems available to the U.S. military. However, growing unrest due to injustice, economic hardships, censorship and dictatorship fueled by the growing tide of fundamentalist Islam led to increasing demonstrations against the unpopular Shah who fled the country and by April 1, 1979 Iran had officially become an Islamic state.Throughout this revolution in Iran, Sullivan served as the chief diplomat in Iran and served as the primary messenger between the administration of US President Jimmy Carter and the Shah. Sullivan felt strongly from very early in the process that the US should abandon its support of the Shah and move to form an alliance with Khomeini. But this view was not shared nor accepted in Washington. As revolution gained momentum, Sullivan became increasingly opposed to policy coming from Washington, to the point of carrying out the directives of the president only half-heartedly. Carter later said in an interview that Sullivan was "specifically insubordinate" and that he should have fired him earlier. Sullivan was replaced in the spring of 1979 by Charge' d'Affaires Bruce Laingen who later became one of 52 hostages during the Iran Hostage Crisis. Sullivan had seved in Laos and Philippines before Iran. Later published Mission to Iran; a memoir of his time as Ambassador.The US embassy in Tehran was shut down in 1979 and never hosted another ambassador again.